In general, a medical blood pump used in medical devices such as ventricular assist devices and extracorporeal circulation support devices may be divided into a pulsatile flow type and a continuous flow type. Here, a centrifugal blood pump which is the continuous flow type has a simpler structure than that of the pulsatile flow type and excellent mechanic performance and thus is widely used for the extracorporeal circulation support device which is used for a short period of time.
In the above described centrifugal blood pump, a one-sided impeller is mostly used to secure a space for forming magnetic coupling, and a space having a relatively thin gap exists at a side where the magnetic coupling is disposed. In the space, a flow does not occur so that when the impeller rotates at high speed, a pressure difference generates between the upper part of the pump and the space and thereby, performance of the pump may be significantly lowered.
In order to prevent this, when a penetration hole which penetrates a space between the upper part and the lower part is formed in the impeller, a flow occurs from the upper part to lower part and thus, above described problem may be solved. However, in such structure, when blood flows through the penetration hole, the blood may remain inside the penetration hole and thus, a thrombus may be formed. In order to prevent this, although the penetration hole is sealed, the sealed part may be damaged or cracked and a thrombus may be also formed.
Also, in terms of performance of the centrifugal blood pump, hemodynamic performance and blood compatibility are especially important. In order to generate sufficient blood flow rate, an impeller having a blade needs to be rotated at high speed. However, rotation of the impeller at high speed may cause damage to blood cells and thus blood compatibility may become worse. Accordingly, development on a blood pump which may prevent damage to blood cells and generate sufficient blood flow rate by rotating an impeller having a blade at low speed is needed.